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Published May 2000 | public
Journal Article

Molecular Evolution of Two Paralogous Tandemly Repeated Heterochromatic Gene Clusters Linked to the X and Y Chromosomes of Drosophila melanogaster

Abstract

Here we report the peculiarities of molecular evolution and divergence of paralogous heterochromatic clusters of the testis- expressed X-linked Stellate and Y-linked Su(Ste) tandem repeats. It was suggested that Stellate and Su(Ste) clusters affecting male fertility are the amplified derivatives of the unique euchromatic gene βCK2tes encoding the putative testis-specific β-subunit of protein kinase CK2. The putative Su(Ste)-like evolutionary intermediate was detected on the Y chromosome as an orphon outside of the Su(Ste) cluster. The orphon shows extensive homology to the Su(Ste) repeat, but contains several Stellate-like diagnostic nucleotide substitutions, as well as a 10-bp insertion and a 3′ splice site of the first intron typical of the Stellate unit. The orphon looks like a pseudogene carrying a drastically damaged Su(Ste) open reading frame (ORF). The putative Su(Ste) ORF, as compared with the Stellate one, carries numerous synonymous substitutions leading to the major codon preference. We conclude that Su(Ste) ORFs evolved on the Y chromosome under the pressure of translational selection. Direct sequencing shows that the efficiency of concerted evolution between adjacent repeats is 5–10 times as high in the Stellate heterochromatic cluster on the X chromosome as that in the Y-linked Su(Ste) cluster, judging by the frequencies of nucleotide substitutions and single-nucleotide deletions.

Additional Information

© 2000 by the Society for Molecular Biology and Evolution. Accepted January 5, 2000. We thank Y. Shevelyov for critical comments and V. E. Alatortsev for improvement of the text. We also thank two anonymous reviewers, through whose comments the manuscript was considerably improved. This work was supported by grants from the Russian Foundation of Basic Research (98-04-49107 and 99-04-48561) and the Russian program Frontiers in Genetics (99-1-069).

Additional details

Created:
August 19, 2023
Modified:
October 20, 2023